using ZB.MOM.WW.Secrets.Abstractions;
using ZB.MOM.WW.Secrets.Rotation;

namespace ZB.MOM.WW.Secrets.Cli.Interactive;

/// <summary>The per-row verdict of a KEK diagnosis.</summary>
public enum RowKekStatus
{
    /// <summary>The session KEK matches the row and successfully unwraps it — the row is healthy.</summary>
    Ok,

    /// <summary>The row is wrapped under a different KEK than the session's — the session cannot open it.</summary>
    WrongKek,

    /// <summary>
    /// The row's <c>kek_id</c> matches the session KEK, yet the DEK unwrap / decrypt fails closed —
    /// the wrap envelope or sealed body is damaged.
    /// </summary>
    Corrupt,
}

/// <summary>One row's KEK verdict: its name, status, and the <c>kek_id</c> it is actually wrapped under.</summary>
/// <param name="SecretName">The secret's normalized name.</param>
/// <param name="Status">Whether the session KEK opens the row (<see cref="RowKekStatus"/>).</param>
/// <param name="RowKekId">
/// The <c>kek_id</c> stamped on the row — the key an operator must hunt down when the status is
/// <see cref="RowKekStatus.WrongKek"/>.
/// </param>
public sealed record KekDiagnosis(string SecretName, RowKekStatus Status, string RowKekId);

/// <summary>
/// The full diagnosis: the session's KEK id and the per-row verdicts (ordered by name), including
/// tombstoned rows since they still carry a KEK-wrapped DEK and block a rewrap-all.
/// </summary>
/// <param name="SessionKekId">The <c>kek_id</c> of the KEK the session is currently using.</param>
/// <param name="Rows">The per-row verdicts, ordered by secret name.</param>
/// <param name="Total">
/// The number of rows scanned from the store (including tombstones). A value greater than
/// <see cref="Rows"/> count means some rows vanished between the metadata list and the per-row fetch
/// (a concurrent hard-absence) and were dropped — the discrepancy makes that visible rather than silent.
/// </param>
public sealed record KekDoctorReport(string SessionKekId, IReadOnlyList<KekDiagnosis> Rows, int Total)
{
    /// <summary>Whether every diagnosed row opens cleanly under the session KEK.</summary>
    public bool Healthy => Rows.All(r => r.Status == RowKekStatus.Ok);
}

/// <summary>
/// Lockout triage: verifies the session KEK actually opens every stored row and drives the rewrap
/// remedy. An operator whose app can no longer decrypt its secrets runs the doctor to learn, per row,
/// which KEK each row is wrapped under and whether the session KEK opens it, then remedies the
/// wrong-KEK rows with a guided rewrap-all onto the session KEK.
/// </summary>
/// <remarks>
/// The store surface makes a full decrypt probe possible even for tombstoned rows:
/// <see cref="ISecretStore.ListAsync"/> enumerates all rows' metadata (including tombstones with
/// <c>includeDeleted: true</c>) and <see cref="ISecretStore.GetAsync"/> returns the full ciphertext
/// row for any name <b>including a tombstoned one</b>, so every row — live or dead — is probed the
/// same way. Plaintext produced by the probe is discarded immediately and never surfaced.
/// </remarks>
public sealed class KekDoctor
{
    /// <summary>
    /// Diagnoses every stored row (including tombstones) against the session KEK: a row whose
    /// <c>kek_id</c> differs from the session KEK is reported <see cref="RowKekStatus.WrongKek"/>
    /// with no decrypt attempted; a row whose <c>kek_id</c> matches is decrypt-probed and reported
    /// <see cref="RowKekStatus.Ok"/> or, if the unwrap fails closed, <see cref="RowKekStatus.Corrupt"/>.
    /// </summary>
    /// <param name="session">The open session; must not be degraded (a KEK is required).</param>
    /// <param name="ct">A token to cancel the diagnosis.</param>
    /// <returns>A <see cref="KekDoctorReport"/> with the per-row verdicts, ordered by name.</returns>
    /// <exception cref="ArgumentNullException"><paramref name="session"/> is <see langword="null"/>.</exception>
    /// <exception cref="InvalidOperationException">
    /// The session is degraded (no KEK / cipher). The operator must re-open the session supplying a
    /// master key before the doctor can probe rows.
    /// </exception>
    public async Task<KekDoctorReport> DiagnoseAsync(SecretsSession session, CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(session);

        if (session.MasterKey is null || session.Cipher is null)
        {
            throw new InvalidOperationException(
                "The session is degraded: no master key (KEK) is available, so rows cannot be probed. " +
                "Re-open the session and supply the key material (for example, paste it at the prompt).");
        }

        string sessionKekId = session.MasterKey.KekId;

        // ListAsync gives metadata only; GetAsync fetches the full ciphertext row (tombstones included)
        // for the decrypt probe. Enumerate ALL rows so tombstones — which still block a rewrap-all — show.
        IReadOnlyList<SecretMetadata> all =
            await session.Store.ListAsync(includeDeleted: true, ct).ConfigureAwait(false);

        List<KekDiagnosis> rows = [];
        foreach (SecretMetadata meta in all.OrderBy(m => m.Name.Value, StringComparer.Ordinal))
        {
            ct.ThrowIfCancellationRequested();

            // Fetch the FRESH row and classify from ITS kek_id — never the (possibly stale) list
            // metadata. A concurrent re-wrap between the list and this fetch would otherwise mislabel a
            // moved row (a benign WrongKek row read as Corrupt, or a re-homed row read as WrongKek).
            StoredSecret? row = await session.Store.GetAsync(meta.Name, ct).ConfigureAwait(false);
            if (row is null)
            {
                // Vanished between the list and the fetch (a concurrent hard-absence). Not added to
                // rows; the Total-vs-Rows.Count gap in the report keeps the drop visible.
                continue;
            }

            rows.Add(Classify(row, sessionKekId, session.Cipher));
        }

        return new KekDoctorReport(sessionKekId, rows, all.Count);
    }

    // Classifies a single FRESH row against the session KEK. A row under a different kek_id is
    // WrongKek (reported with its own id so the operator knows which key to hunt) and is NOT decrypted;
    // a matching row is decrypt-probed (plaintext discarded at once) → Ok, or Corrupt if it fails closed.
    private static KekDiagnosis Classify(StoredSecret row, string sessionKekId, ISecretCipher cipher)
    {
        if (!string.Equals(row.KekId, sessionKekId, StringComparison.Ordinal))
        {
            return new KekDiagnosis(row.Name.Value, RowKekStatus.WrongKek, row.KekId);
        }

        try
        {
            _ = cipher.Decrypt(row);
            return new KekDiagnosis(row.Name.Value, RowKekStatus.Ok, row.KekId);
        }
        catch (SecretDecryptionException)
        {
            return new KekDiagnosis(row.Name.Value, RowKekStatus.Corrupt, row.KekId);
        }
    }

    /// <summary>
    /// Remedies wrong-KEK rows by re-wrapping every row from <paramref name="oldKek"/> onto the
    /// session's KEK, delegating to <see cref="KekRotationService.RewrapAllAsync"/> (idempotent, and
    /// fail-closed on rows wrapped by neither the old nor the session KEK).
    /// </summary>
    /// <param name="session">The open session; must not be degraded (its KEK is the rewrap target).</param>
    /// <param name="oldKek">The provider for the KEK the wrong-KEK rows are currently wrapped under.</param>
    /// <param name="ct">A token to cancel the pass (already-persisted re-wraps are retained).</param>
    /// <returns>A <see cref="RewrapReport"/> summarizing the pass (no secret material).</returns>
    /// <exception cref="ArgumentNullException">
    /// <paramref name="session"/> or <paramref name="oldKek"/> is <see langword="null"/>.
    /// </exception>
    /// <exception cref="InvalidOperationException">The session is degraded (no KEK / cipher).</exception>
    public Task<RewrapReport> RewrapAllAsync(
        SecretsSession session, IMasterKeyProvider oldKek, CancellationToken ct)
    {
        ArgumentNullException.ThrowIfNull(session);
        ArgumentNullException.ThrowIfNull(oldKek);

        if (session.MasterKey is null || session.Cipher is null)
        {
            throw new InvalidOperationException(
                "The session is degraded: no master key (KEK) is available to re-wrap onto. " +
                "Re-open the session and supply the key material before running the rewrap remedy.");
        }

        return new KekRotationService(session.Store, session.Cipher)
            .RewrapAllAsync(oldKek, session.MasterKey, ct);
    }
}
